What would the consequinces be if Japan didn't attack Pearl Harbor?
The US would then not attack Japan and Battle of Mid-Way,Naval Blockade on Japan Mainland,US would not join the Allies and dropping of Little Boy and Fat Man would not take place. However, the colonial master of South East Asia like Britain, France (In Indo-China,Now is termed as Vietnam),Dutch East Indies (Indonesia) and USA (Phillipines) would simply attack Japan when Hitler and Mussolini failed their mission and Japan might lose because Russia by then had also declared war on Japan, invading Manchuria which was the important income source.
How did Pearl Harbor attack Japan?
You have some serious reading to do. Pearl Harbor did not attack Japan. The US Naval Base at Pearl Harbor HI was attacked by the Japanese on Dec 7, 1941. The American ships were tied up at their morring points in the harbor, and there had been no declaration of war. This was an unprovoked attack by Japan on the United States.